Category: Building Things

So… here we are. It’s been a little over a week since I started this project. Lots of ups, downs, laughs, tears, fist-shaking, face-palming, thumbs-upping, head hung in defeat, and arms raised in victory. I gave up on the Raspberry Pi Zero/Arduino combination (curse you, Timer3!!!) and switched to a Raspberry Pi Pico microcontroller (which, aside from making an LED blink by copy-pasting an example a few months ago, I knew nothing about) and started the electronics from scratch. By yesterday evening, things were moving along again. And in the end…

I failed.

It was pretty close, though. By this morning, my little robot could move around on its own and successfully detect and turn to avoid (some) obstacles using an HC-SR04 ultrasonic rangefinder. I was working on LED rangefinding and cliff sensing when I ran out of time.

Head bowed and properly ashamed, I told my wife that my robot sweeper wasn’t ready. She assured me that it was “cute” and thanked me for not setting the house on fire. Then, a twist: she’s been doing a ton of research into the little robots and based on the layout of our house and the stuff we have kicking around, she’s not sure which one would be a good fit. We even talked about getting a (gasp) cordless stick vacuum instead. Personally, I’d still rather have a robot because neither of us enjoy vacuuming or sweeping (does anyone?) and it’s more likely to get done if a computer does it.

Regardless, the sale is now over and we didn’t buy anything. Which means… I have more time. It’s not really a challenge anymore since we don’t know when the next good sale will be (or even what we want) but as it’s been quite the learning experience and we both agree that having a cheap little sweeper robot can’t hurt, I’m going to keep working on this project.

I have also “discovered” the Pi Pico. I’ve had a couple of them for a while now but since most of the stuff I do is with an Arduino, they’d been sitting around until I had time to tinker with them. Well, in the last 48 hours or so I’ve tinkered with them until my eyes would no longer focus and I’ve got to say that I’m quite pretty extremely impressed. Setting up MicroPython was easy, it’s easy to program with Python, and it has so many peripherals built in (not to mention the PIO stuff which I haven’t tried but looks great) that it’s… well… pretty amazing. And I’ve barely scratched the surface. I’ve got a million other project ideas for it, and it could well become my go-to when I need a microcontroller for something.

With the time constraint relaxed (at least for now), I’m very interested in seeing where this project goes. But now it’s late again and I really, REALLY need to clean my piles of components, wires, and papers off the dining room table before I go to bed.

Well… things aren’t looking great at this point.

I thought I had everything figured out. Raspberry Pi Zero was going to talk over I2C and a level shifter with two Arduino Pro Micros – one for sensors and one for motors.

Rangefinder and LED/phototransistor pairs were working great and reporting nicely back to the Pi over I2C.

I wasn’t worried about the motors because a couple of days ago I had the drive motors working when sending commands using the USB serial on the Arduino (that’s what I was doing in the video from the other day).

But alas, the USB serial port uses timers differently than I2C on the Arduino, and the servos and I2C are arguing over the same 16-bit timer hardware in the 32U4. There is one other 16-bit timer on the chip (Timer3) but when I tried using it instead of Timer1 for the servos it doesn’t have the same kind of access to the pins that Timer1 has.

I think, anyway. The best I could get out of the servos was an occasional irregular “putt”. And now it’s getting late and I’ve spent way too much time staring at datasheets. Oh, and of course when I went to the Arduino forums I was greeted with this today:

I know there’s a solution, but my old worn-out brain can’t think of it right now. I guess I could run the sensors over I2C and the motors over UART, but I was hoping for a cleaner, less confusing setup. A different microcontroller? ESP32? Pico? Ehurrrghhh.

At any rate, I need to get to bed. Lots of stuff I’ve been putting off that I should really do tomorrow before I get back to work on this particular project.

I can’t believe I’m saying this, but… IT’S ALIIIIIVEEE!

Doesn’t do much more than drive around with commands sent through a terminal session to the onboard Pi Zero, but I’m pretty sure this is the best run at building a robot I’ve had.

Needs better wheels, though – shiny hard plastic drive wheels aren’t so good on carpet, and a front “wheel” made out of a big blob of masking tape leaves a lot to be desired.

But there is definitely some progress going on. And it already picked up some hair (and there’s no brush or mop or vacuum on it)!

Woohoo little robot!

Okay, so I’m making some progress. I looked around on the internet to see if I could get some ideas for what I wanted and I came up with this:

After some intense pencil & paper work, some printing, and some fumbling with little screws, I’ve got this:

Frankly, it’s pretty disappointing compared to the first picture but at least it’s progress.

My plan at this point is to use a Raspberry Pi Zero as the “brain”, and use an Arduino Pro Micro to handle the motor PWM because the Pi’s software PWM can be jittery. I need to figure out how to get it moving, how to control it, and how to keep itself from throwing itself down the stairs or getting jammed in a corner under the couch. Oh, and power it without an extension cord. Oh, and get it to actually sweep the floor.

No problem – only five things. Should be easy.

So… last night I made a wheel. It’s not a particularly nice wheel, but it’s wheel-y and should do the job. Not a lot of progress, I’ll admit, but I have lots of time.

Or, at least I thought I did.

Just a few minutes ago I got a text from my wife – she’s at the store and they have a sale on little robot vacuums that ends in seven days.

Seven days!